The present disclosure relates to a solids transport system that can be used in a flue gas desulfurization system, particularly one using a dry scrubber structure (e.g., a circulating dry scrubber (CDS) or novel integrated desulfurization scrubber (NIDS)). Dry powders or particles are transported using fluidized surfaces, and recycled hot flue gas is used as the fluidizing gas for such surfaces. This permits heating components to be reduced in size or fewer in number, reducing capital costs and operating costs.
During combustion, the chemical energy in a fuel is converted to thermal heat, which can be used in various forms for different applications. The fuels used in the combustion process can include a wide range of solid, liquid, and gaseous substances, including coal, oil (diesel, No. 2, Bunker C or No. 6), natural gas, wood, tires, biomass, etc.
Combustion transforms the fuel into a large number of chemical compounds. Water (H2O) and carbon dioxide (CO2) are the primary products of complete combustion. However, other combustion reactions with chemical components in the fuel result in undesirable byproducts. Depending on the fuel used, such byproducts may include particulates (e.g., fly ash), acid gases such as sulfur oxides (SOx) or nitric oxides (NOx), metals such as mercury or arsenic, carbon monoxide (CO), and hydrocarbons (HC). The emissions levels of many of these byproducts are regulated by governmental entities, such as the U.S. Environmental Protection Agency (EPA).
Several different technologies exist for removing such byproducts from the flue gas. In one method, known as spray drying chemical absorption or dry scrubbing, an aqueous alkaline solution or slurry, which has been finely atomized, is sprayed into the hot flue gas downstream of the combustion chamber in which the fuel was combusted. The alkaline reagent reacts with the pollutants, and particulates are formed. The water evaporates and cools the hot flue gas. The exiting cleaned flue gas typically has a moisture content of about 10% to about 15%. The flue gas then travels to a particulate collection device, generally a baghouse, where the particulates are removed from the flue gas, which is then sent to a stack.
In a flue gas desulfurization (FGD) system, particularly one including a circulating dry scrubber (CDS), the solid particles captured in the particulate collection device are usually recycled back to the dry scrubber to improve reaction efficiency. The particles typically travel back to the dry scrubber over fluidized surfaces. Heated, pressurized ambient air is generally used as the fluidizing gas. The air is commonly pressurized using a fan/blower, and heated using an electric resistance heater. These heaters consumer enormous amounts of power, on the order of hundreds of kilowatts. The heating elements add significant capital costs and operating costs to the overall system. It would be desirable to provide alternative CDS-FGD systems that can reduce such costs as well as improve or maintain combustion byproduct removal.